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Developmet of Phono-mediated Terahertz Detectors using Superconducting Tunnel Junctions

使用超导隧道结的声介导太赫兹探测器的开发

基本信息

批准号：
15360040
负责人：
OTANI Chiko
金额：
$ 9.79万
依托单位：
RIKEN
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-15360040/
关键词：
Terahertz wave Detector Superconducting Tunnel Junction Phonon-mediated detector

项目摘要

First, we fabricated a phonon-mediated terahertz detector using superconducting tunnel junctions (STJs). The layer structure is Nb/Al/AlOx/Al/Nb fabricated on LiNbO_3 and LiTaO_3 substrates. The sizes ranged from 5 to 200μm square. The subgap leakage current at 4.2, 1.5 and 0.35K showed the similar values with the STJs fabricated on conventional Si and sapphire substrates. This means that the new substrates can be used in high-performance terahertz detector. Then, we designed and made a new optical components for our cryostat. Using this setup, we irradiated pulsed terahertz waves and read the signals from the detectors through a charge-sensitive preamplifier. We successfully detected the corresponding pulse signals for the first time. In addition, we confirmed that the rise time of the pulse signal was relatively long, showing that the detection process was consistent with the phonon-mediated detection.Next, we analyzed the detected pulse shapes and found that one pulse included two different pulses with the relatively short and long risetime, respectively. They were distinguished by applying the time derivative of the output charge. Combined this result with X-ray measurements, they were identified as the events directly absorbed with the superconducting electrode and the phonon-mediated events. We also checked the frequency response and confirmed the flat spectral response in 1-2 THz.Moreover, we introduced (1) thicker substrates for increasing the efficiency, (2) a series array detector to increase the detection area, and (3) the STJs with larger bottom electrode and smaller top electrode. In (1), we observed the increase of the efficiency. In (2), we could not get the greater signal. In (3), we fabricated STJs with the different size from 25-70μm and evaluated the mean free path of the quasiperticles inside the superconducting electrode.

首先，我们制作了一个声子介导的太赫兹探测器使用超导隧道结（STJs）。在LiNbO_3和LiTaO_3衬底上制备了Nb/Al/AlOx/Al/Nb层状结构。大小范围为5 ~ 200μm见方。在4.2，1.5和0.35K下的亚带隙漏电流显示出与常规Si和蓝宝石衬底上制备的STJ相似的值。这意味着这种新型衬底可以用于高性能的太赫兹探测器。在此基础上，我们设计并制作了一种新型的光学元件。使用这种设置，我们照射脉冲太赫兹波，并通过电荷敏感的探测器读取来自探测器的信号。我们首次成功地探测到了相应的脉冲信号。此外，我们还证实了脉冲信号的上升时间相对较长，这表明该探测过程与声子介导的探测过程相一致。接下来，我们对探测到的脉冲波形进行了分析，发现一个脉冲包含两个不同的脉冲，分别具有相对较短和较长的上升时间。通过应用输出电荷的时间导数来区分它们。结合X射线测量结果，我们将它们确定为直接被超导电极吸收的事件和声子介导的事件。此外，为了提高效率，我们采用了（1）较厚的衬底，（2）串联阵列探测器，以增加探测面积，以及（3）具有较大底部电极和较小顶部电极的STJ。在（1）中，我们观察到效率的增加。在（2）中，我们无法获得更大的信号。在（3）中，我们制作了25-70μm不同尺寸的STJ，并计算了超导电极内准超导体的平均自由程。